Am I all right? Why do doctors wear green or blue clothes while doing an operation? Look at the first picture. Stare at the dot for 10 seconds. Then look at the second picture. What can you see? What you see is called afterimage. Afterimage is an image that continues to appear in people's vision after the image has disappeared. The blood is red. But if you look at blood for a long time, you will be affected by afterimage. Doctors change their scrubs from white into green because green may help doctors see the room clearly after staring at blood for a long time.